Numerous pharmaceutical substances are available for administration to animals, including humans, for a variety of purposes. These substances include, for example, therapeutic agents, such as drugs; dietary supplements, such as vitamins; prophylactic agents, such as antigens for use in vaccines; and diagnostic agents, such as labeled imaging agents. Administration of these substances can be via a number of routes including intramuscular, subcutaneous and oral administration. Intramuscular and subcutaneous administration of the substance suffer from disadvantages. For example, specialized skills are required to administer the pharmaceutical; large scale administration can be difficult to perform; it is expensive; and a number of side reactions can occur to the substance administered. There are biologically active agents, for example certain dietary supplements, drugs, hormones and immunogens, whose efficacy almost totally is lost upon oral administration. Included among those agents that cannot be effectively orally administered are polypeptide agents. Oral delivery of certain protein and polypeptide drugs and other biological agents is complicated by the presence of proteolytic digestive enzymes in the stomach and intestines. Unprotected proteins, which are administered orally, are largely degraded by such enzymes before they are passed through the enteric wall and enter blood circulation. Many such agents cannot be formulated in water; there are numerous agents that, upon exposure to water, are not stable. Thus, there continues to be a need for the development of compositions and methods for delivery of such substances to animals, including humans.